And yet, not many know how she died and why it is significant - until now.

A British nurse working in Brussels during World War I, she assisted Allied soldiers who had become separated from their units and were trapped behind the advancing German front.

This was heroism in some eyes but the Germans regarded it as a sin worthy only of death.

Yes, it is terrible to execute a woman... but think what would become of a nation at war if it should allow it to go unpunished

Herr Zimmerman, German Under Secretary for Foreign Affairs

Although not involved in espionage, she was tried by a German court martial and executed by firing squad for her actions.

Her files, released on Thursday by the Public Record Office, show photographs of her grave and place of execution.

They also include a letter from the Countess of Borchgrave, sent to the nurse's mother in Norfolk warning the woman not speak to anyone about her daughter's whereabouts for fear she would be found.

The letter arrived the day after Edith's execution.

The countess's husband had been in Brussels at the time - August 1915 to December 1917 - and had said it was "extremely dangerous" for an Englishwoman to be within a country occupied by the German Army.

'Best efforts'

But on 13 October 1915, a telegram was sent from the American minister in Brussels to the American ambassador in London.

It read: "At two o'clock this morning, despite our best efforts, which continued until the last moment, Miss Cavell was sentenced and executed."

Edith Louisa Cavell was born on 4 December 1865 in Swardeston, Norfolk, the daughter of the local vicar.

Aged 20 she entered the nursing profession and in 1907 she became the matron of the Berkendael Institute in Brussels.

The Public Record Office released Cavell's files on Thursday

It was there that she hid British, French and Belgian soldiers until they were helped to escape to Holland, which was neutral.

Although Cavell had made a full confession her execution was widely condemned.

Neutral governments, including the US and Spanish representatives, sought a reprieve for her and a Belgian, Philippe Baucq, but to no avail.

Her files show she could have returned to England at the start of the war, in September 1914, as about 70 nurses left at that time with the US ambassador.

But she chose to remain in her post.

In the record is a report from Herr Zimmerman, German Under-Secretary for Foreign Affairs.

He responded to what he called "great sensation" in European newspapers to Cavell's death, and says: "Yes it is terrible that it should be necessary to execute a woman, but think for one moment what would become of a nation at war if it should allow to go unpunished one who has committed a crime against its Army's safety - even if that one happens to be a woman."